Terminologically perhaps, but terminology is mutable, and the limits are often porous and/or fuzzy.
Why, though? Who gets to say "this is how you ought to do it, and no other way!", and by what justification? I get that it might be a problem if it means you CAN'T group, but that's not the case here - you totally can still do everything in groups, either directly (actually in a party) or indirectly (just interacting with other players while not in an actual party). You can just ALSO do it solo, for a large part, but that solo option doesn't take anything away from people who'd choose otherwise.
Seems to me you're just too hung up on the terminology maybe? Who cares, really, what label you put on things - it's about the actual experience.
That's a more cogent example, but it's also a conceptual difference in design - WoW puts a stronger emphasis on instanced content over world content, and for very clear reasons: it's easier to control, easier to balance, and provides and overall more satisfying experience as a result, especially at higher tiers of difficulty. Let's not forget that a big reason why some other titles have better public events is because they're less popular; that's not to say they're "worse" or anything nonsensical like that, but they're more niche in the sense that the players who choose these games tend to be more invested, and as a result, tend to play along better. If you tried that in a title like WoW, the amount of disruptive elements from players who aren't as invested in the fantasy would make those events FAR less successful.
And you still play with other people in WoW. In fact a lot of the content you straight CAN'T DO without other people (edge cases like some Dk soloing an M+ in 10 hours aside). Your problem seems to be that for a lot of low-difficulty content, you CAN do it without other people; but you can still do it with groups, and many people do. So you're really just complaining about 1) the label they put on the game, which is a category that's always been subject to fuzzy definitions; and 2) that somehow other people are playing differently from what you'd expect and even though this doesn't impact your experience directly this seems to bother you for some reason.
I'm not sure what to tell you there other than to perhaps re-examine what your own framework is really doing to your thinking here.